Why Do Cats Require Magnesium?

Magnesium (Mg) is one of the essential macrominerals that cats require for optimal health. Other macrominerals (required in larger amounts) that these animals require are phosphorus, calcium, chloride, potassium, sodium, and sulfur.

Naturally, this mineral is available in some foods. However, it is often added to some commercial cat foods, sold as a dietary supplement, and some medicines have it especially laxatives, antacids, some phosphorus binders.

Some of the foods rich in Mg include cheese, yogurt, milk, and other dairy products, sardines, salmon, dark leafy greens, legumes, nuts and seeds (especially pumpkin, chia, and flax seeds).

About 67% of magnesium in cats’ bodies is stored in bones and the remainder is in intracellular compartments and fluid including blood plasma.

Finally, the blood plasma has about 1% of the total magnesium in a cat’s body of which around 20-30% is bound to proteins while the remainder either in ionized form Mg2+(62%) or bound to citrates, phosphates and other compounds.

Sources of magnesium
Sources of magnesium

Absorption and homeostasis

Magnesium intestinal absorption is mainly through active transport. However, diffusion can also occur if there is a concentration gradient between extracellular compartments and the lumen.

The amount absorbed is influenced by its dietary content, hormones (like parathyroid hormone), vitamin D, dietary content of phosphate, oxalates, potassium, zinc, and proteins among other factors.

For instance, high calcium and phosphorus decrease their absorption. Also, since phytates bind to Mg, they can affect its absorption.

Intestinal absorption and kidney help in keeping magnesium hemostasis. In the kidney, this mineral is filtered at glomerulus while reabsorption occurs in the proximal convoluted tubules, the loop of Henle and distal tubules according to required amounts.

Finally, aldosterone and thyroxine promote its loss in urine and feces while parathyroid hormone promotes its intestinal absorption and renal resorption and mobilization from bones.

Is magnesium in cat food necessary – functions

Yes. It is very necessary since it has many vital functions in a cat’s body which include the following:

  • It is a cofactor for many enzymes involved in many vital biochemical reactions including cellular respiration, energy production, protein synthesis, synthesis RNA, DNA, glutathione, among others.
  • For normal heartbeat rhythm, muscle contraction and impulse transmission, it plays a role in the active transportation of potassium and calcium through the cell membrane as well as the production and destruction of the neurotransmitter acetylcholine.
  • It has a structural role in the cell membrane and bone mineral.
  • It is involved in some hormone secretion and functioning
  • It promotes the absorption of vitamin C and E, potassium, sodium, calcium and phosphorus.


It helps in stomach acid buffering and as a laxative in case of constipation. Its salts (including citrate, hydroxide, sulfate) draws water into the GI tract and improves gut motility due to its role in muscle functioning. However, these salts or magnesium polyethylene glycols aren’t recommended in managing constipation. There are superior treatments.

Magnesium dosage or requirement

The AAFCO recommends that cat foods have a minimum 0.08% magnesium for growth and reproduction and 0.04% for adult maintenance based on dry matter

Basing on metabolizable energy, the recommended minimum amount is 0.2g and 0.1g per 1000 kcal ME for growth or reproduction and adult maintenance respectively.

However, there is one condition specified by AAFCO which is provided that “the mean urine pH of cats fed ad libitum is not below 6.4, the risk of struvite urolithiasis increases as the magnesium content of the diet increases.”

Deficiency signs

Although we have mentioned that about 50% of magnesium is found in bones, it cannot be readily mobilized to help curb deficiency in blood serum. Therefore, if enough is not availed in blood, a deficiency is possible.

Low calcium in cats or hypomagnesemia is associated with symptoms such as

  • Poor growth
  • Convulsions
  • Ataxia, muscle weakness and severe pain (tetany), muscle twitching and tremors. Also, less muscle growth is often noted in kittens
  • Carpal joint overextension
  • Depression
  • Arrhythmias

Some of the causes include intestinal malabsorption disorders, chronic malnutrition, diabetes mellitus, drugs poisonous to kidneys such as nephrotoxic, excessive loss via urine after the use of diuretics, less intake or low magnesium in cat food.

High magnesium in cats

Hypermagnesemia or elevated blood Mg2+ level is a life-threatening condition that is uncommon in healthy cats.

Some of its symptoms include nausea, vomiting, struvite urinary stones if the pH goes high, weakness, low heart rate, paralysis, reflex abnormalities, reduced respiration, cardiac arrest, coma among others.

Common causes include kidney failure, constipation, hypothyroidism, hyperthyroidism, hypoadrenocorticism and IV fluids or medications that have magnesium (including antacids, some laxatives, and so on).

Magnesium and cat urinary struvite formation

There has been an erroneous assumption that high magnesium contributed to the formation of struvite or magnesium ammonium phosphate uroliths.

However, factors such as urine concentration, pH and presence calculogenic materials (made from cellular, extracellular materials together with minerals especially calcium phosphate) can potentially cause these uroliths.

Magnesium supplements for cats

Most commercial cat diets have enough amounts of this mineral as it is added to meet the required amounts. Also, as WikiVet notes “meat meals, meat and bone meals, cereal products, and soybean meal,” are a good source.

If your cat lacks enough amounts, you can consider magnesium citrate, sulfate, chloride, oxide, and carbonate or ground limestone (which also has calcium).

Also, try some brands such as Rivas Remedies magnesium for cats, some multivitamin and multimineral such as Zoeez Naturals Total Wellness, Complete for Cats by VitaPaws™ 180 sprinkle capsules, Multivitamin for Dogs and Cats among others.


There is little literature on the use of magnesium oil for cats including how to use it and its safety. In humans, it is used as a spray for transdermal absorption (bypasses GI tract).

See also

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